Field
Exemplary embodiments relate to a liquid crystal display device.
Discussion of the Background
A liquid crystal display device is a type of flat panel display device that is formed of two substrates on which electrodes are formed, and a liquid crystal layer is inserted therebetween. The liquid crystal display device may adjust an amount of transmitted light by applying a voltage to the electrodes to rearrange liquid crystal molecules of the liquid crystal layer.
The liquid crystal display device may have a structure in which an electric field generating electrode is formed on each of the two substrates. A plurality of thin film transistors and a pixel electrode may be arranged in a matrix form on a first substrate (lower panel, a display panel of a thin film transistor), and red, green, and blue color filters may be formed on the second substrate (upper panel, a common electrode display panel), and a common electrode may be disposed covers the entire surface of the second substrate.
However, by disposing the pixel electrode and the color filters on different substrates in the liquid crystal display device as described above, the pixel electrode and the color filters may not be accurately aligned with respect to each other and cause an alignment error. To solve this, a color filter on array (or COA), a structure in which the color filters and the pixel electrode are formed on the same substrate, has been suggested.
Also, considering an adhesion margin when adhering a first substrate and a second substrate, a light blocking member such as a black matrix may have a relatively greater size. However, an aperture ratio may be decreased due to the increased size of the black matrix, and thus, the black matrix may be formed on the first substrate.
A cell gap, which refers to a gap between liquid crystal layers between the two substrates, may affect the overall operating characteristics of the liquid crystal display device such as a response speed, a contrast ratio, an angle of view, luminance uniformity, and the like. If the cell gap is not uniform, a uniform image may not be displayed over the entire screen and cause image quality defects. Thus, in order to maintain a uniform cell gap over the entire region on the substrates, a plurality of spacers are formed on at least one of the two substrates.
The plurality of spacers may include a main column spacer that substantially supports the two substrates and a sub-column spacer assisting the function of the main column spacer.
For process simplification, a light blocking member such as a black matrix and a spacer may be simultaneously formed. The light blocking member, the main column spacer, and the sub-column spacer may be simultaneously formed by forming multiple step differences.
Generally, a step difference between a main column spacer and a sub-column spacer formed may be about 0.5 μm. A uniform density ratio of column spacers may provide a process margin against active unfilled area (AUA) defects during a liquid crystal process.
A step protruding having a height equivalent to the height of the column spacers in regions of other than the main column spacer and the sub-column spacer may function as a sub-column spacer, resulting in a change in the entire density of the main column spacer and the sub-column spacer. This may cause a problem in a liquid crystal margin at a low temperature.
Thus, a liquid crystal display device capable of providing a uniform density of spacers is required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.